Making water last

Scientists convened in downtown Sacramento last week to discuss technological advances that might help California achieve a sustainable water strategy for the future.

On August 1, leading researchers from the Lawrence Berkeley National Laboratory said developments in conservation and desalinization are being carefully developed for the state’s specific needs. The lab is a member of the National Academy of Sciences and has produced research that’s led to 13 Nobel prizes. Among the speakers was Peter Nico, who works in its Resilient Energy, Water and Infrastructure program.

“As California whiplashes back and forth between drought and floods, what can we do to balance out those humps?” Nico posited. “We over-draft 1- to 2 million-acre feet of water a year in California.”

One answer to Nico’s question, he said, is a new sensor technology that his lab is developing to scan and monitor farm soil, identifying which areas of subsurface naturally hold large amounts of groundwater and which ones don’t. Nico said this image-viewing technology can give California farmers more ability to access groundwater on their lands. Nico later acknowledged that convoluted water rights and general concerns about over-drawing underground aquifers could complicate using the tech.

Another speaker, Berkeley lab chemist Chinmayee Subban, says she has been in constant contact with central and coastal California growers as she develops charge-based desalinization methods for brackish groundwater. Subban called brackish flows under the surface an almost entirely untapped water source in California. Her team has been developing a process of using low-cost electrodes to desalinate the brackish groundwater in a way that’s high-yielding and energy efficient.

“We’re evaluating the scientific and engineering challenges right now,” Subban said of the research. “And we’re looking for how we can use California’s excess solar power to run this.”

Dan Miller of the lab’s Chemical Sciences Division said another desalinization technology, reverse osmosis, is also advancing. Miller observed that this process for cleaning water has become dramatically less energy consumptive in recent years, particularly if the water is coming from ideal soil conditions.

While reverse osmosis tech can remove 99.7 percent of salt, it still struggles to remove toxic compounds that are naturally occurring in soils, which often means the water has to be run through the process twice. That costs twice the energy to make sure problems don’t occur, like rice crops being contaminated with arsenic. Miller said the Berkeley lab is developing a new technology to extract those toxic compounds the first time the water runs through the system.